RESOLUTION OF UNMIXED BIPARTITE GRAPHS

Mohammadi, Fatemeh,Moradi, Somayeh Korean Mathematical Society 2015 대한수학회보 Vol.52 No.3

Let G be a graph on the vertex set $V(G)=\{x_1,{\cdots},x_n\}$ with the edge set E(G), and let $R=K[x_1,{\cdots},x_n]$ be the polynomial ring over a field K. Two monomial ideals are associated to G, the edge ideal I(G) generated by all monomials $x_i,x_j$ with $\{x_i,x_j\}{\in}E(G)$, and the vertex cover ideal $I_G$ generated by monomials ${\prod}_{x_i{\in}C}{^{x_i}}$ for all minimal vertex covers C of G. A minimal vertex cover of G is a subset $C{\subset}V(G)$ such that each edge has at least one vertex in C and no proper subset of C has the same property. Indeed, the vertex cover ideal of G is the Alexander dual of the edge ideal of G. In this paper, for an unmixed bipartite graph G we consider the lattice of vertex covers $L_G$ and we explicitly describe the minimal free resolution of the ideal associated to $L_G$ which is exactly the vertex cover ideal of G. Then we compute depth, projective dimension, regularity and extremal Betti numbers of R/I(G) in terms of the associated lattice.

Electrochemical and anticorrosion behavior of functionalized graphite nanoplatelets epoxy coating

Somayeh Mohammadi,Faramarz Afshar Taromi,Homeira Shariatpanahi,Jaber Neshati,MAHMOUD HEMMATI 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.6

Functionalized graphite nanoplatelets (FGNP) were used as efficient and compatible nano-particles toproduce homogenous epoxy nano-coating with impressive anticorrosion behavior for carbon steel. Thecharacterizations of the nano-particle and nano-coating were carried out by SEM, FT-IR, XRD, TEM andpull-off test. Fine distribution of nano-particles in the cured nano-coating with particle sizes of 20–40 nm was obtained. Electrochemical experiments, salt spray and X-ray fluorescence showed that thenano-coatings protect the metal substrate by formation of passive layer and physical barriercharacteristics. Three samples (0.25%, 0.5% and 1%) of FGNP-epoxy coatings were prepared that 0.5%showed better anticorrosion properties.

Prediction of the bond strength of ribbed steel bars in concrete based on genetic programming

Emadaldin Mohammadi Golafshani,Alireza Rahai,Seyedeh Somayeh Hosseini Kebria 사단법인 한국계산역학회 2014 Computers and Concrete, An International Journal Vol.14 No.3

This paper presents the application of multi-gene genetic programming (MGP) technique for modeling the bond strength of ribbed steel bars in concrete. In this regard, the experimental data of 264 splice beam tests from different technical papers were used for training, validating and testing the model. Seven basic parameters affecting on the bond strength of steel bars were selected as input parameters. These parameters are diameter, relative rib area and yield strength of steel bar, minimum concrete cover to bar diameter ratio, splice length to bar diameter ratio, concrete compressive strength and transverse reinforcement index. The results show that the proposed MGP model can be alternative approach for predicting the bond strength of ribbed steel bars in concrete. Moreover, the performance of the developed model was compared with the building codes' empirical equations for a complete comparison. The study concludes that the proposed MGP model predicts the bond strength of ribbed steel bars better than the existing building codes' equations. Using the proposed MGP model and building codes' equations, a parametric study was also conducted to investigate the trend of the input variables on the bond strength of ribbed steel bars in concrete.

RESOLUTION OF UNMIXED BIPARTITE GRAPHS

Fatemeh Mohammadi,Somayeh Moradi 대한수학회 2015 대한수학회보 Vol.52 No.3

Let G be a graph on the vertex set V (G) = {x1, . . . , xn} with the edge set E(G), and let R = K[x1, . . . , xn] be the polynomial ring over a field K. Two monomial ideals are associated to G, the edge ideal I(G) generated by all monomials xixj with {xi, xj} ∈ E(G), and the vertex cover ideal IG generated by monomials ∏xi∈C xi for all minimal vertex covers C of G. A minimal vertex cover of G is a subset C ⊂ V (G) such that each edge has at least one vertex in C and no proper subset of C has the same property. Indeed, the vertex cover ideal of G is the Alexander dual of the edge ideal of G. In this paper, for an unmixed bipartite graph G we consider the lattice of vertex covers LG and we explicitly describe the minimal free resolution of the ideal associated to LG which is exactly the vertex cover ideal of G. Then we compute depth, projective dimension, regularity and extremal Betti numbers of R/I(G) in terms of the associated lattice.

Synthesis and characterization of CdS/Bi2S3 nanocomposite via simple microwave approach

Mohammad Ebadi,Somayeh Abedini,Omid Rezai,Mosleh Mohammadi Rad 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.5

CdS/Bi2S3 nanocomposite was synthesized successfully via microwave method. Different parameters such as time effect, power effect and precursor concentration effect were investigated on product size and morphology. The products were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Also the optical properties of synthesized sample were investigated by UV–vis diffuse reflectance spectroscopy (DRS).

Comparison of mice’ sperm parameters exposed to some hazardous physical agents

Mohammad-Bagher Abdollahi,Somayeh Farhang Dehghan,Faezeh Abasi Balochkhaneh,Manouchehr Ahmadi Moghadam,Hamzeh Mohammadi 환경독성보건학회 2021 환경독성보건학회지 Vol.36 No.3

The present study was aimed to compare the effects of exposure to noise, vibration, lighting, and microwave on male mice’ sperm parameters. The mice were randomly assigned to five groups of eight, which comprised of the unexposed group and exposure groups including the lighting (1000 lux), noise (100 dB(A)), vibration (acceleration of 1.2 m/s²) and microwave (power density of 5 watts). The exposure groups were subjected to the four agents for 8 hours a day, 5 days a week during a 2-week period. Semen analysis were done according to World Health Organization guidelines. The highest significant mean difference in sperm count (-1.35×10<SUP>6</SUP>/mL) had being observed between the microwave group and the control one (P=0.001). The highest difference in immotile percent (25.88 %) had being observed between the noise group and the control one (P=0.001). The highest difference in normal morphology (-27.06 %) observed between the lighting exposure group and the control group (P=0.001). The four agents can cause changes in different sperm parameters, however for definite conclusion; more laboratory and field studies are required. In total, exposure to microwave has had the greatest effect on sperm count and exposure to light has had the greatest effect on normal morphology and non-progressive motility. Moreover, exposure to noise has had the greatest effect on progressive motility and immotile percent, respectively.

Prototype of a Peak to Average Power Ratio Reduction Scheme in Orthogonal Frequency Division Multiplexing Systems

( Pooria Varahram ),( Borhanuddin Mohd Ali ),( Somayeh Mohammady ),( Ahmed Wasif Reza ) 한국인터넷정보학회 2015 KSII Transactions on Internet and Information Syst Vol.9 No.6

Peak to average power ratio (PAPR) is one of the main imperfections in the broadband communication systems with multiple carriers. In this paper, a new crest factor reduction (CFR) scheme based on interleaved phase sequence called Dummy Sequence Insertion Enhanced Partial Transmit Sequence (DSI-EPTS) is proposed which effectively reduces the PAPR while at the same time keeps the total complexity low. Moreover, the prototype of the proposed scheme in field programmable gate array (FPGA) is demonstrated. In DSI-EPTS scheme, a new matrix of phase sequence is defined which leads to a significant reduction in hardware complexity due to its less searching operation to extract the optimum phase sequence. The obtained results show comparable performance with slight difference due to the FPGA constraints. The results show 5 dB reduction in PAPR by applying the DSI-EPTS scheme with low complexity and low power consumption.

Free vibration analysis of FG porous joined truncated conical-cylindrical shell reinforced by graphene platelets

Kiarasi, Faraz,Babaei, Masoud,Mollaei, Somayeh,Mohammadi, Mokhtar,Asemi, Kamran Techno-Press 2021 Advances in nano research Vol.11 No.4

Natural frequency analysis of functionally graded porous joined truncated conical-cylindrical shell reinforced by graphene platelet is investigated in this paper. The structure is consisting of a layered model with five kinds of distribution of graphene platelets in a metallic matrix containing open-cell interior pores. To calculate the effective properties of the porous nanocomposite joined shell, the generalized rule of mixture and the modified Halpin-Tsai equations are employed. Four different porosity distributions are assumed along the shell thickness: two kinds of symmetric functionally graded distributions, non-symmetric functionally graded distributions and uniform distribution of porosity. Graded finite element method (GFEM) based on Rayleigh-Ritz energy formulation has been used to solve 2D- axisymmetric elasticity equations. A parametric study is also conducted to show the effects of different geometric parameters, boundary conditions, weight fraction of graphene platelets, porosity coefficient, distribution of porosity and dispersion pattern of graphene platelets on the natural frequencies and mode shapes of the structure.